The present invention relates to a real time apparatus for checking a total penetration weld and more specifically relates to checking the weld of a joint which cannot be observed by direct observation. The apparatus according to the invention is more particularly intended for checking welds on a substantially closed member or the welding of two long, small diameter tubes.
Assembly by total penetration welding leads, at the back of the weld, to the formation of a luminous molten bath, e.g. in the case of TIG or MIG welding, or to the formation of a luminous or light plasma constituted by metal vapours ionized to a greater or lesser extent, in the case of welding by electron or laser beam and optionally accompanied by fine molten metal droplets. Establishing these phenomena during welding makes it possible to ensure that the molten area has covered the entire thickness of the members to be assembled.
An apparatus for the real time checking of a total penetration weld comprises in per se known manner an optoelectronic means for detecting the light intensity at the back of the weld bead to the right of the welding spot, means for processing the electric signal supplied by said detection means and a signaling means.
A detection means is known, which is constituted by a box containing an optoelectronic detector and an optical processing means. This is a voluminous detection means, which can only be used when the back of the welding bead is easily observable.
A detection means is also known, which is constituted by a group of photodiodes and a detection means constituted by a group of optical fibres connected to a photodiode. In these two known detection means, the group of photodiodes and the group of optical fibres are arranged so as to detect a light signal on a circumference. In these known detection means, each photodiode or optical fibre constitutes a substantially omnidirectional detector. The number of photodiodes or optical fibres necessary for observing the complete welding bead is high. Thus, these detection means are voluminous and cannot be used for checking a total penetration weld of a joint which is difficult to directly observed.